Inverter control devices, electric power steering systems, electric vehicle systems

Abstract

To reduce a direct-current component or low-order harmonic component of an inverter output current that occurs in an operational state of a motor having less PWM pulse counts.SOLUTION: An inverter controller 200 comprises a PWM pulse generation unit 250 for generating a PWM pulse signal Pr for controlling an inverter 100 for each prescribed control period. The PWM pulse generation unit 250 generates the PWM pulse signal Pr so that at least three or more pulses are present in one cycle of the fundamental wave of the output voltage of the inverter 100, and further a pulse generation condition that the on / off state of the PWM pulse signal Pr is switched at a zero-cross point where the fundamental wave changes across 0 is met, while generating the PWM pulse signal asynchronous to the control period.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an inverter control device, and an electric power steering system and an electric vehicle system using the inverter control device. [Background technology]

[0002] Inverter control devices that use PWM (pulse width modulation) control to control inverter drive and drive motors are widely used. In such inverter control devices, a technique is known in which the inverter is operated in an overmodulation mode (overmodulation region) in which the inverter output voltage command exceeds the inverter's maximum output level (sine wave) to increase the motor speed, and in a one-pulse mode (one-pulse region) in which the PWM pulse train is connected to form one pulse in order to further increase the output voltage.

[0003] When an inverter control device is operated from the overmodulation region to the single-pulse region, a voltage error occurs in the inverter output, and the DC and ripple components contained in the inverter output current increase, causing motor output torque fluctuations and noise and vibration.Therefore, there is a demand for technology that suppresses the voltage error in the region that transitions from the overmodulation region to the single-pulse region and reduces the DC and ripple components of the current.

[0004] Regarding reduction of current ripple in the overmodulation region, the technology of Patent Document 1 is known. Patent Document 1 describes an inverter device that generates PWM pulses when performing trapezoidal wave modulation using a trapezoidal wave in the overmodulation region so that the integrated values ​​of the areas of the on-pulses and off-pulses of a plurality of PWM pulses in the inversion region of the modulated wave that changes from the bottom to the top of the trapezoidal wave are equal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-19458 A Summary of the Invention [Problem to be solved by the invention]

[0006] The technology of Patent Document 1 cannot appropriately control the periodicity of the pulse train that repeats in a positive / negative (180 degree) cycle of the modulated wave in a motor operating state where the number of PWM pulses is reduced, which may cause an error in the inverter output voltage and increase the DC component and low-order harmonic components in the inverter output current. [Means for solving the problem]

[0007] The inverter control device according to the present invention generates a PWM pulse signal for controlling an inverter. I live The PWM pulse generating unit generates a PWM pulse Selecting either a synchronous mode or an asynchronous mode, and in the asynchronous mode, The PWM pulse signal is generated so as to satisfy the pulse generation conditions that there are at least three pulses in one period of the fundamental wave of the inverter output voltage, and the on / off state of the PWM pulse signal switches at the zero-crossing point where the fundamental wave changes across zero. An electric power steering system according to the present invention includes an inverter control device, an inverter controlled by the inverter control device, and an AC motor driven by the inverter, and controls steering of a vehicle using the AC motor. An electric vehicle system according to the present invention includes an inverter control device, an inverter controlled by the inverter control device, and an AC motor driven by the inverter, and runs using the driving force of the AC motor. Effect of the Invention

[0008] According to the present invention, it is possible to reduce the DC components and low-order harmonic components of the inverter output current that are generated in an operating state of the motor where the number of PWM pulses is reduced. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram showing the configuration of a motor device having an inverter control device according to a first embodiment of the present invention. [Diagram 2] 1 is a block diagram showing a functional configuration of a PWM pulse generating unit according to a first embodiment of the present invention. [Diagram 3] FIG. 2 is an explanatory diagram of a method for generating an asynchronous pulse signal according to the first embodiment of the present invention. [Figure 4] 1 is a diagram showing an asynchronous pulse signal over a range of one period of a modulated wave signal. [Diagram 5] 3 is a flowchart of PWM pulse control according to the first embodiment of the present invention. [Figure 6] FIG. 7 is an explanatory diagram of a method for generating an asynchronous pulse signal according to a second embodiment of the present invention. [Figure 7] 1 is a diagram showing an asynchronous pulse signal over a range of one period of a modulated wave signal. [Figure 8] 10 is a flowchart of PWM pulse control according to a second embodiment of the present invention. [Figure 9] 1 is a configuration diagram of an electric power steering device to which an inverter control device is applied. [Figure 10] FIG. 1 is a configuration diagram of an electric vehicle to which an inverter control device is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention provides an inverter control device that controls an inverter by PWM control, and when performing PWM pulse control according to a modulation method (sine wave modulation, two-phase modulation, trapezoidal wave modulation, etc.) in order to reduce, for example, battery power consumption and heat generation of an inverter in an operating state of a motor where the number of PWM pulses is smaller than a predetermined value, the inverter control device generates PWM pulse edges at timings corresponding to the zero crossings of a modulated wave, and outputs PWM pulses that maintain symmetry in a PWM pulse train of a 180-degree period of the modulated wave, thereby reducing the DC component and low-order harmonic components of the inverter output current and increasing the output of the inverter. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] (First embodiment) 1 is a block diagram showing the configuration of a motor device 1 having an inverter control device 200 according to a first embodiment of the present invention. The motor device 1 is connected to a battery 2, and has an inverter 100, an inverter control device 200, and a motor 300.

[0012] The battery 2 is a DC voltage source for the inverter 100. The DC voltage DCV of the battery 2 is converted by the inverter 100 into a three-phase AC voltage with variable voltage and variable frequency, and is applied to the motor 300.

[0013] The motor 300 is a synchronous motor that is rotationally driven by the supply of a three-phase AC voltage. A rotational position sensor 320 is attached to the motor 300 in order to control the phase of the three-phase AC voltage applied to the motor 300 from the inverter 100 to match the phase of the induced voltage of the motor 300. Here, the rotational position sensor 320 may be, for example, a resolver composed of an iron core and a winding. Alternatively, the rotational position sensor 320 may be composed of a GMR sensor or a Hall element.

[0014] The inverter control device 200 includes a current control unit 210 , a PWM pulse generating unit 250 , a drive signal generating unit 260 , a rotational position detecting unit 270 , and a current detecting unit 280 .

[0015] The rotational position detection unit 270 detects the rotational position θ of the rotor in the motor 300 based on the output signal of the rotational position sensor 320 .

[0016] The current detection unit 280 acquires the three-phase current detection values ​​(Iu, Iv, Iw) flowing through the motor 300 from the current sensor Ict, and obtains the dq-axis current detection values ​​(Id, Iq) by performing three-phase / two-phase conversion on these current detection values ​​based on the rotational position θ detected by the rotational position detection unit 270.

[0017] The inverter control device 200 has a current control function for controlling the output of the motor 300. The current control unit 210 outputs voltage commands (Vd*, Vq*) so that the current detection values ​​(Id, Iq) detected by the current detection unit 280 match the current command values ​​(Id*, Iq*) input from a higher-level controller (not shown).

[0018] The PWM pulse generating unit 250 performs three-phase pulse width modulation (PWM) using the voltage commands (Vd*, Vq*) calculated by the current control unit 210, the direct current voltage DCV of the battery 2, the rotational position θ, and a predetermined carrier frequency fc that has been set in advance, and generates a PWM pulse signal Pr for controlling the inverter 100. A specific method for generating the PWM pulse signal Pr by the PWM pulse generating unit 250 will be described later.

[0019] The drive signal generating unit 260 converts the PWM pulse signal Pr generated by the PWM pulse generating unit 250 into a drive signal DR and outputs it to the inverter 100. The inverter 100 has a plurality of semiconductor switch elements corresponding to each phase of the three-phase AC voltage, and each semiconductor switch element is controlled to be turned on / off by the drive signal DR. As a result, the output voltage of the inverter 100 is adjusted according to the control of the inverter control device 200.

[0020] In the above, an example of the configuration of the motor device 1 when controlling the current of the motor 300 according to a current command from a higher-level controller has been described with reference to Fig. 1, but the configuration of Fig. 1 can also be applied when other control methods are adopted. For example, when controlling the rotation speed of the motor 300, the motor rotation speed ωr is calculated based on the time change in the rotation position θ, and a voltage command or current command is generated so that it matches the speed command from the higher-level controller. Also, when controlling the output torque of the motor 300, a relational expression or map between the motor current (Id, Iq) and the motor torque is used to generate current commands (Id*, Iq*).

[0021] Next, a detailed description will be given of a method for generating the PWM pulse signal Pr by the PWM pulse generating unit 250. Fig. 2 is a block diagram showing a functional configuration of the PWM pulse generating unit 250 according to the first embodiment of the present invention.

[0022] 2, the PWM pulse generating unit 250 has the following functional blocks: a modulation factor calculating unit 51, a rotation speed calculating unit 52, a pulse phase angle calculating unit 53, a voltage phase calculating unit 54, a phase change width calculating unit 55, a pulse setting unit 56, a dq / three-phase converting unit 57, a carrier wave calculating unit 58, a PWM control unit 59, and a PWM control mode determining unit 60. The inverter control device 200 including the PWM pulse generating unit 250 is configured by, for example, a microcomputer, and can realize these functional blocks by executing a predetermined program in the microcomputer. Alternatively, some or all of these functional blocks may be realized by using hardware circuits such as logic ICs and FPGAs.

[0023] The modulation factor calculation unit 51 calculates the modulation factor MF of the output voltage of the inverter 100 based on the DC voltage DCV of the battery 2 and the voltage commands (Vd*, Vq*) by the following formula (1). Note that the modulation factor MF represents the voltage amplitude ratio between the DC power supplied from the battery 2 to the inverter 100 and the AC power output from the inverter 100 to the motor 300.

number

[0024] The rotation speed calculation unit 52 calculates the motor rotation speed ωr, which indicates the rotation speed (revolutions) of the motor 300, from the change over time of the rotation position θ. The motor rotation speed ωr may be a value expressed as either an angular velocity (rad / s) or a rotation speed (rpm). These values ​​may also be converted into each other for use.

[0025] The pulse phase angle calculation unit 53 calculates a pulse phase angle α for switching the on / off state of the PWM pulse signal Pr based on the modulation factor MF calculated by the modulation factor calculation unit 51. Here, a plurality of pulse phase angles α are calculated according to the number of pulses N of the PWM pulse signal Pr included in one period of the fundamental wave of the output voltage of the inverter 100. For example, when the number of pulses N=3, the pulse phase angles α1, α2, α1', α2' expressed by the following equations (2) to (5), respectively, are calculated. This makes it possible to set each pulse width of the PWM pulse signal Pr based on the modulation factor MF. α1=arccos{(1+MF) / 2} ···(2) α2=π-α1 (3) α1'=π+α1 (4) α2'=2π-α1 (5)

[0026] The pulse number N can be set to, for example, an odd number of at least 3, and is preset in the inverter control device 200. Alternatively, the user may set it arbitrarily, or the number may be arbitrarily switched depending on the operating state of the motor 300. The number of pulse phase angles α calculated by the pulse phase angle calculation unit 53 is determined depending on the pulse number N, and the larger the pulse number N, the larger the number of pulse phase angles α. In this embodiment, a case where the pulse number N is 3 will be described.

[0027] Based on the voltage commands (Vd*, Vq*) and the rotational position θ, the voltage phase calculation unit 54 calculates a voltage phase θv corresponding to the phase angle of the voltage output by the inverter 100 with respect to the current command values ​​(Id*, Iq*) input from the upper controller. Here, the voltage phase θv is calculated, for example, by the following equation (6). θv=θ+arctan(Vq* / Vd*) ···(6)

[0028] The phase change width calculation unit 55 calculates a phase change width Δθ of the output voltage of the inverter 100 in a control period of the inverter control device 200. Here, the control period of the inverter control device 200 refers to a period in which the PWM pulse generation unit 250 generates the PWM pulse signal Pr, and is set in advance according to the calculation performance of the microcomputer constituting the inverter control device 200 and the accuracy required for controlling the motor 300. The phase change width calculation unit 55 calculates the phase change width Δθ based on the motor rotation speed ωr and a preset carrier frequency fc, for example, by the following formula (7). Δθ=ωr / fc (7)

[0029] The pulse setting unit 56 sets the timing of each pulse edge present in the current control cycle based on the pulse phase angle α, voltage phase θv, and phase change width Δθ calculated from the equations (2) to (7), respectively. Then, in accordance with the timing of each pulse edge that has been set, the signal voltage is changed from on to off or from off to on, respectively, to generate an asynchronous pulse signal P. The asynchronous pulse signal P generated by the pulse setting unit 56 will be described in detail later.

[0030] The dq / three-phase conversion unit 57 performs three-phase conversion on the voltage commands (Vd*, Vq*) based on the rotational position θ, and calculates three-phase voltage commands Vu*, Vv*, Vw* (U-phase voltage command value Vu*, V-phase voltage command value Vv*, and W-phase voltage command value Vw*). This makes it possible to generate three-phase voltage commands Vu*, Vv*, Vw* as modulated wave signals for three-phase AC voltages. Note that by selecting a modulation method other than sine wave modulation, the three-phase voltage commands Vu*, Vv*, Vw* may be generated with waveforms other than sine waves, such as trapezoidal waves or waveforms in which harmonics of a predetermined order are superimposed on a sine wave.

[0031] The carrier wave calculation unit 58 determines a synchronous carrier frequency fcs synchronized with the rotation of the motor 300 based on the motor rotation speed ωr, and generates a carrier wave Tr that changes periodically at this synchronous carrier frequency fcs. The carrier wave Tr may be either a triangular wave or a sawtooth wave. In addition, when the carrier frequency fcs is 15 times or more higher than the rotation frequency of the motor 300, the carrier frequency fcs does not need to be synchronized with the rotation of the motor 300.

[0032] The PWM control unit 59 uses the carrier wave Tr output from the carrier wave calculation unit 58 to pulse width modulate each of the three-phase voltage commands Vu*, Vv*, Vw* output from the dq / three-phase conversion unit 57, and generates a synchronization pulse signal P' synchronized with the control period (carrier wave Tr). Hereinafter, this will be simply referred to as the synchronization pulse signal P'.

[0033] The PWM control mode determination unit 60 selects either the asynchronous pulse signal P generated by the pulse setting unit 56 or the synchronous pulse signal P' generated by the PWM control unit 59 based on the modulation factor MF and the motor rotation speed ωr. Then, the selected asynchronous pulse signal P or synchronous pulse signal P' is output to the drive signal generation unit 260 as the PWM pulse signal Pr by the PWM pulse generation unit 250.

[0034] Specifically, for example, when the modulation factor MF and the motor rotation speed ωr are within a predetermined range, the PWM control mode determination unit 60 selects a synchronous mode in which a pulse signal is synchronized with the control period, and outputs the synchronous pulse signal P' as the PWM pulse signal Pr. On the other hand, when the modulation factor MF and the motor rotation speed ωr are outside the predetermined range, the PWM control mode determination unit 60 selects an asynchronous mode in which a pulse signal is asynchronous with the control period, and outputs the asynchronous pulse signal P as the PWM pulse signal Pr. That is, the PWM control mode determination unit 60 selectively outputs either the asynchronous pulse signal P or the synchronous pulse signal P' as the PWM pulse signal Pr based on the operating state of the motor 300. Note that, regardless of whether the synchronous mode or the asynchronous mode is selected, any modulation method can be used from among modulation methods such as sine wave modulation, two-phase modulation, and trapezoidal wave modulation.

[0035] Next, the asynchronous pulse signal P will be described in detail. In general pulse width modulation performed by the PWM control unit 59, a synchronous pulse signal P' is generated as a PWM pulse signal Pr based on a comparison result between a carrier wave Tr and a modulated wave signal. In contrast, the asynchronous pulse signal P generated as a PWM pulse signal Pr by the pulse setting unit 56 is generated directly from the result of calculation performed in the PWM pulse generating unit 250, without using the carrier wave Tr or the modulated wave signal. Specifically, the pulse phase angle calculation unit 53, the voltage phase calculation unit 54, and the phase change width calculation unit 55 perform calculations using the above-mentioned equations (2) to (7), respectively, to obtain a pulse phase angle α, a voltage phase θv, and a phase change width Δθ, and the pulse setting unit 56 sets the timing of each pulse edge for each control period using these calculation results, thereby generating the asynchronous pulse signal P, which is a PWM pulse asynchronous with the control period. Hereinafter, it will be simply called the asynchronous pulse signal P.

[0036] 3 is an explanatory diagram of a method for generating an asynchronous pulse signal P according to the first embodiment of the present invention. In FIG. 3, the graph shown in (a) represents the counter value of a PWM timer, the graph shown in (b) represents a modulated wave signal, and the graph shown in (c) shows an example of a PWM pulse train output as the asynchronous pulse signal P. The counter value of the PWM timer shown in FIG. 3(a) corresponds to a carrier wave Tr generated by a carrier wave calculation unit 58.

[0037] In the pulse setting unit 56, as shown in FIG. 3(a), for example, a PWM timer whose counter value increases and decreases periodically with a constant carrier period Tc is used to generate the asynchronous pulse signal P. At this time, by making the carrier period Tc constant regardless of the motor rotation speed ωr, the timing of the control process related to the generation of the asynchronous pulse signal P can be made asynchronous with the control period while being synchronized with the rotation of the motor 300. Note that in the example of FIG. 3, an example of a sawtooth-wave up-count timer in which the counter value increases from 0 to the maximum value MaxCount at a constant rate and the counter value is reset to 0 for each carrier period Tc according to the timing of the control process is shown, but other types of PWM timers may be used as long as the value increases and decreases periodically with a constant carrier period Tc. For example, a down-count timer whose counter value changes according to a waveform obtained by inverting an up-count timer upside down, or a triangular wave timer whose counter value increases and decreases at a constant rate, can also be used as the PWM timer in the pulse setting unit 56.

[0038] When the asynchronous pulse signal P generated in the PWM pulse generating unit 250 is output to the drive signal generating unit 260 as the PWM pulse signal Pr, the inverter control device 200 performs control processing in synchronization with the carrier period Tc shown in Fig. 3(a). Specifically, the current detecting unit 280 samples and holds the detection signal of the current sensor Ict at a timing synchronized with the carrier period Tc to obtain the current detection values ​​(Iu, Iv, Iw). The rotational position detecting unit 270 detects the output signal of the rotational position sensor 320 at a timing synchronized with the carrier period Tc to obtain the rotational position θ. Then, the above-mentioned calculation is performed for each carrier period Tc using these obtained values, thereby generating the asynchronous pulse signal P.

[0039] In addition, in the sample & hold operation of the detection signal of the current sensor Ict performed by the current detection unit 280, a voltage ripple occurs when the detection signal is charged to the capacitor of the sample & hold circuit, and this voltage ripple is superimposed on the input terminal of the A / D conversion circuit, which may cause A / D conversion noise. The period of this A / D conversion noise is equivalent to the control period (carrier period Tc) of the inverter control device 200. It is also possible to make the detection period of the current detection unit 280 shorter than the control period and obtain a detection signal from the current sensor Ict multiple times per control period, but for the convenience of microcomputer processing, the sampling frequency (reciprocal of the detection period) of the current detection unit 280 needs to be an integer multiple of the control frequency (reciprocal of the control period) of the inverter control device 200. In any case, the integer multiple of the period of the A / D conversion noise can be regarded as the carrier period Tc, which is the period of the PWM timer.

[0040] 3(b) shows an example of a modulated wave signal in the case of trapezoidal wave modulation. The period of this modulated wave corresponds to the fundamental wave period of the output voltage of the inverter 100. As described above, in the PWM pulse generating unit 250, unlike the synchronous pulse signal P' obtained by general pulse width modulation, the asynchronous pulse signal P is obtained directly by calculation. Therefore, the modulated wave signal is not necessarily required when generating the asynchronous pulse signal P.

[0041] 3(c) shows an example of the asynchronous pulse signal P when the number of pulses is set to N=3 in this embodiment. In this embodiment, the asynchronous pulse signal P switches between on / off states at zero crossing points (phase angles 0°, 180°) where the modulated wave crosses 0 and inverts from negative to positive or from positive to negative, and at phase angles α1, α2, α1', α2'. The phase angles α1, α2, α1', α2' are calculated using the above-mentioned equations (2) to (5), respectively.

[0042] The pulse setting unit 56 generates the asynchronous pulse signal P shown in FIG. 3(c) for each carrier period Tc shown in FIG. 3(a) according to a pulse train set in a cycle of an electrical phase angle of 180° based on the zero crossing point of the modulated wave shown in FIG. 3(b). Specifically, for example, when the current control processing timing is the control processing timing Tt(i) in FIG. 3(a), the pulse setting unit 56 generates the asynchronous pulse signal P in a range (phase change width Δθ) from the voltage phase θ(i) corresponding to this control processing timing to the voltage phase θ(i+1) corresponding to the next control processing timing. In the example of FIG. 3(c), since the phase angles α2, α1' and the zero crossing point (phase angle 180°) are included in this range, the timer values ​​corresponding to these phase angles are set in the PWM timer. Then, at the timing when the count value of the PWM timer reaches each of the set timer values, the signal value of the asynchronous pulse signal P is changed from on to off or from off to on, thereby setting a pulse edge and generating the asynchronous pulse signal P.

[0043] FIG. 4 is a diagram showing the asynchronous pulse signal P of FIG. 3(c) in the range of one period (θ=0 to 2π) of the modulated wave signal. As shown in FIG. 4, the asynchronous pulse signal P is obtained by inverting the pulse train waveform in the first half period (θ=0 to π) including pulse phase angles α1 and α2, and the inverted pulse train waveform in the second half period (θ=π to 2π) including pulse phase angles α1' and α2' is the same as the pulse train waveform. In other words, the waveform of the asynchronous pulse signal P is point-symmetrical with respect to the zero crossing point of the modulated wave signal. Therefore, by inverting the pulse train in the first half period, it is possible to set the pulse train in the second half period and generate the asynchronous pulse signal P.

[0044] In the PWM pulse generating unit 250, the voltage phase calculation unit 54 calculates a voltage phase θv corresponding to the voltage phase θ(i) of the current control processing timing. Furthermore, the phase change width calculation unit 55 calculates a phase change width Δθ from the voltage phase θ(i) of the current control processing timing to the voltage phase θ(i+1) of the next control processing timing. Based on these calculated values ​​θv and Δθ, the pulse setting unit 56 sets a timer value corresponding to the pulse edge in the current control processing to the PWM timer, thereby generating an asynchronous pulse signal P according to the pulse phase angle α calculated by the pulse phase angle calculation unit 53.

[0045] 5 is a flowchart of the PWM pulse control according to the first embodiment of the present invention. In this embodiment, the PWM pulse generating unit 250 performs the process shown in the flowchart of FIG. 5 for each predetermined control period according to the carrier period Tc, thereby performing the PWM pulse control and outputting the PWM pulse signal Pr to the drive signal generating unit 260.

[0046] In step S1, the PWM pulse generating unit 250 calculates the modulation factor MF and the motor rotation speed ωr, respectively, using the modulation factor calculation unit 51 and the rotation speed calculation unit 52. Here, the modulation factor MF and the motor rotation speed ωr can be calculated using the above-mentioned equations (1) and (2), respectively.

[0047] In step S2, the PWM pulse generating unit 250 calculates a pulse phase angle α based on the modulation factor MF calculated in step S1 using the pulse phase angle calculation unit 53. Here, the number of times the asynchronous pulse signal P switches between on and off states per one period of the fundamental wave of the inverter output voltage is determined according to a preset pulse number N, and the number of pulse phase angles α to be calculated is determined by subtracting the number of zero crossing points (θ=0, π) of the fundamental wave of the inverter output voltage from the number of switches.

[0048] In this embodiment, since the number of pulses is N=3 as described above, the number of times the asynchronous pulse signal P switches between on and off states per one period of the fundamental wave of the inverter output voltage is calculated to be 2N=6. By subtracting the number of zero-crossing points of the fundamental wave of the inverter output voltage from this number of switches, the number of pulse phase angles α to be calculated is calculated to be 6-2=4. Therefore, the process of step S2 is performed by calculating the four pulse phase angles α1, α2, α1', α2' using the above-mentioned equations (2) to (5).

[0049] In step S3, the PWM pulse generating unit 250 calculates the voltage phase θv by the voltage phase calculation unit 54. Here, based on the voltage commands (Vd*, Vq*) and the rotational position θ input from the current control unit 210 and the rotational position detection unit 270, respectively, the voltage phase θv corresponding to the phase angle of the inverter output voltage is calculated using the above-mentioned equation (6).

[0050] In step S4, the PWM pulse generating unit 250 calculates the phase change width Δθ by the phase change width calculation unit 55. Here, based on the motor rotation speed ωr obtained in step S1 and a predetermined carrier frequency fc according to the control period of the PWM pulse generating unit 250, the phase change width Δθ of the inverter output voltage in the control period of the PWM pulse generating unit 250 is calculated by using the above-mentioned equation (7).

[0051] In step S5, the PWM pulse generating unit 250 sets the timer value (first PWM timer value) according to the pulse phase angles α1, α2, α1', α2' obtained in step S2 to the PWM timer by the pulse setting unit 56. Here, as described above, based on the voltage phase θv and phase change width Δθ obtained in steps S3 and S4, respectively, the voltage phase range of the fundamental wave of the inverter output voltage included in the period from the current control processing timing to the next control processing timing is specified. Then, if there is a zero cross point (zero cross point of the modulated wave) of the fundamental wave of the inverter output voltage and the pulse phase angles α1, α2, α1', α2' obtained in step S2 that are within the specified voltage phase range, the timer value corresponding to that phase angle is set to the PWM timer as the first PWM timer value. Note that, if multiple zero cross points or pulse phase angles are included in the voltage phase range of the fundamental wave of the inverter output voltage, the first PWM timer value is set for each of the multiple zero cross points or pulse phase angles. This makes it possible to set the timing for switching the ON / OFF state of the PWM pulse signal Pr based on the pulse phase angle α, voltage phase θv, and phase change width Δθ determined in steps S2 to S4, respectively.

[0052] In step S6, the PWM pulse generating unit 250 calculates a modulated wave signal for the three-phase AC voltage using the dq / three-phase conversion unit 57. As described above, the voltage commands (Vd*, Vq*) input from the current control unit 210 are subjected to three-phase conversion based on the rotational position θ, thereby generating three-phase voltage commands Vu*, Vv*, Vw* that correspond to the modulated wave signal.

[0053] In step S7, the PWM pulse generating unit 250 performs pulse width modulation based on the modulated wave signal calculated in step S7 using the PWM control unit 59, and sets a timer value (second PWM timer value) corresponding to the result to the PWM timer. Here, the carrier wave Tr generated in synchronization with the rotation of the motor 300 by the carrier wave calculation unit 58 is used to perform well-known pulse width modulation on the modulated wave signal to determine the voltage phase angle of each pulse edge in the synchronous pulse signal P', and sets the timer value corresponding to the voltage phase angle as the second PWM timer value to the PWM timer. Note that when the carrier wave Tr is 15 times or more the rotation of the motor 300, the carrier wave Tr may be asynchronous with the rotation of the motor 300.

[0054] In step S8, the PWM pulse generating unit 250 judges the PWM control mode by the PWM control mode judging unit 60. Here, the operating state of the motor 300 is judged from the modulation factor MF and the motor rotation speed ωr obtained in step S1, respectively, and the PWM control mode suitable for the operating state is judged. Specifically, for example, as described above, when the modulation factor MF and the motor rotation speed ωr are within a predetermined range, it is judged that the synchronous mode, which controls the pulse signal synchronized with the control period, is the optimal PWM control mode. On the other hand, when the modulation factor MF or the motor rotation speed ωr is outside the predetermined range, it is judged that the asynchronous mode, which controls the pulse signal asynchronous with the control period, is the optimal PWM control mode. This makes it possible to select either the synchronous mode or the asynchronous mode as the optimal PWM control mode based on the operating state of the motor 300.

[0055] In step S9, the PWM pulse generating unit 250 determines whether or not the PWM control mode determined in step S8 to be suitable for the operating state of the motor 300 is the asynchronous mode. If the asynchronous mode is selected as the optimal PWM control mode in step S8, the process proceeds to step S10, and if the asynchronous mode is not selected, i.e., if the synchronous mode is selected, the process proceeds to step S11.

[0056] In step S10, the PWM pulse generating unit 250 sets the first PWM timer value set in step S5 as the timer value used to generate the PWM pulse signal Pr. In this case, the asynchronous pulse signal P generated by the pulse setting unit 56 is selectively output from the PWM pulse generating unit 250 as the PWM pulse signal Pr.

[0057] In step S11, the PWM pulse generating unit 250 sets the second PWM timer value set in step S7 as the timer value used to generate the PWM pulse signal Pr. In this case, the synchronous pulse signal P' generated by the PWM control unit 59 is selectively output from the PWM pulse generating unit 250 as the PWM pulse signal Pr.

[0058] After executing the process of step S10 or S11, in step S12, the PWM pulse generating unit 250 generates a PWM pulse signal Pr using either the asynchronous pulse signal P or the synchronous pulse signal P', and outputs it to the drive signal generating unit 260. That is, when step S10 is executed, the asynchronous pulse signal P generated by the pulse setting unit 56 is output as the PWM pulse signal Pr, and when step S11 is executed, the synchronous pulse signal P' generated by the PWM control unit 59 is output as the PWM pulse signal Pr. This makes it possible to selectively output either the asynchronous pulse signal P or the synchronous pulse signal P' depending on the operating state of the motor 300.

[0059] After completing the process of step S12, the PWM pulse control shown in the flowchart of Fig. 5 is stopped and the process waits until a predetermined control period has elapsed. When the predetermined control period has elapsed and the next control timing arrives, the PWM pulse generating unit 250 resumes the process shown in the flowchart of Fig. 5 from step S1 and repeats the PWM pulse control.

[0060] Second Embodiment Next, a second embodiment of the present invention will be described. In this embodiment, a case where the number of pulses N per fundamental wave period of the inverter output voltage in the asynchronous pulse signal P is 5 will be described. Note that the configurations of the inverter control device and the motor control device, and the functional configuration of the PWM pulse generation unit in the inverter control device in this embodiment are the same as those in FIGS. 1 and 2 described in the first embodiment. Therefore, the following description of this embodiment will be made using the configurations of FIGS. 1 and 2.

[0061] FIG. 6 is an explanatory diagram of a method for generating an asynchronous pulse signal P according to a second embodiment of the present invention. In FIG. 6, the graph shown in (a) represents the counter value of the PWM timer, the graph shown in (b) represents the modulation wave signal, and the graph shown in (c) shows an example of a PWM pulse train output as the asynchronous pulse signal P. Note that the graphs in FIGS. 6(a) and 6(b) are the same as the graphs in FIGS. 3(a) and 3(b) described in the first embodiment, respectively.

[0062] FIG. 6(c) shows an example of the asynchronous pulse signal P when the number of pulses is N = 5 in this embodiment. In the asynchronous pulse signal P in this embodiment, the on / off state of the signal is switched at the zero cross points (phase angles 0° and 180°) where the modulation wave crosses 0 and reverses from negative to positive or from positive to negative, and at the pulse phase angles α1, α2, α3, α4, α1’, α2’, α3’, α4’.

[0063] Among the above pulse phase angles, the pulse phase angles α1, α2, α1’, α2’ are respectively obtained by the formulas (2) to (5) described in the first embodiment. Also, for the pulse phase angles α3, α4, α3’, α4’, they are respectively obtained by the following formulas (8) to (11). In formula (8), p is an arbitrary number where 0 < p < 1 and is preset. α3 = p × α1 ···(8) α4 = π - α3 ···(9) α3’ = π + α3 ···(10) α4’ = 2π - α3 ···(11)

[0064] FIG. 7 is a diagram showing the asynchronous pulse signal P of FIG. 6(c) in the range of one period (θ=0 to 2π) of the modulated wave signal. As shown in FIG. 7, the asynchronous pulse signal P is obtained by inverting the pulse train waveform in the first half period (θ=0 to π) including pulse phase angles α1, α2, α3, and α4, and the inverted pulse train waveform in the second half period (θ=π to 2π) including pulse phase angles α1', α2'α3', and α4'. That is, in this embodiment as in the first embodiment, the waveform of the asynchronous pulse signal P is point-symmetrical with respect to the zero crossing point of the modulated wave signal. Therefore, it is possible to set the pulse train in the second half period by inverting the pulse train in the first half period and generate the asynchronous pulse signal P.

[0065] 8 is a flowchart of PWM pulse control according to the second embodiment of the present invention. In this embodiment, the PWM pulse generating unit 250 performs PWM pulse control by executing the process shown in the flowchart of FIG. 8 for each predetermined control period according to the carrier period Tc, and outputs a PWM pulse signal Pr to the drive signal generating unit 260.

[0066] In the flowchart of Fig. 8, the same steps as those in the flowchart of Fig. 5 described in the first embodiment are assigned the same step numbers. In the following, the description of the steps having the same step numbers as those in Fig. 5 will be omitted unless otherwise necessary.

[0067] In step S2A, the PWM pulse generating unit 250 calculates a pulse phase angle α based on the modulation factor MF calculated in step S1 using the pulse phase angle calculation unit 53. Here, similar to the first embodiment, the number of times the asynchronous pulse signal P switches between on and off states per one period of the fundamental wave of the inverter output voltage is determined according to a preset pulse number N, and the number of pulse phase angles α to be calculated is determined by subtracting the number of zero crossing points (θ=0, π) of the fundamental wave of the inverter output voltage from the number of times the asynchronous pulse signal P switches.

[0068] In this embodiment, since the number of pulses is N=5 as described above, the number of times that the asynchronous pulse signal P switches between on and off states per one period of the fundamental wave of the inverter output voltage is calculated to be 2N=10. By subtracting the number of zero crossing points of the fundamental wave of the inverter output voltage from this number of times of switching, the number of pulse phase angles α to be calculated is found to be 10-2=8. Therefore, the process of step S2A is performed by calculating the four pulse phase angles α1, α2, α1', and α2' using the above-mentioned equations (2) to (5), respectively, and calculating the four pulse phase angles α3, α4, α3', and α4' using the above-mentioned equations (8) to (11), respectively.

[0069] In step S5A, the PWM pulse generating unit 250 sets the timer value (first PWM timer value) corresponding to the pulse phase angles α1, α2, α3, α4, α1', α2', α3', α4' obtained in step S2A to the PWM timer by the pulse setting unit 56. Here, similar to the first embodiment, the voltage phase range of the fundamental wave of the inverter output voltage included in the period from the current control processing timing to the next control processing timing is specified based on the voltage phase θv and the phase change width Δθ obtained in steps S3 and S4, respectively. Then, if there is a zero cross point (zero cross point of the modulated wave) of the fundamental wave of the inverter output voltage and the pulse phase angles α1, α2, α3, α4, α1', α2', α3', α4' obtained in step S2A that exists within the specified voltage phase range, the timer value corresponding to that phase angle is set to the PWM timer as the first PWM timer value. This makes it possible to set the timing for switching the ON / OFF state of the PWM pulse signal Pr based on the pulse phase angle α, voltage phase θv, and phase change width Δθ calculated in steps S2A to S4, respectively.

[0070] As described above, in the embodiment of the present invention, the PWM pulse generating unit 250 generates a PWM pulse signal asynchronous with the control period while generating the PWM pulse signal Pr so as to satisfy the pulse generation conditions that at least three or more pulses exist in one period of the fundamental wave of the inverter output voltage in a region near the zero-crossing including the zero-crossing point of the modulated wave, and the on / off state of the PWM pulse signal switches at the zero-crossing point where the fundamental wave of the inverter output voltage changes across zero. As a result, it is possible to reduce the DC component and low-order harmonic components of the motor current generated in an operating state where the number of pulses in the PWM pulse signal Pr is small, thereby making it possible to reduce noise and vibration of the motor 300.

[0071] Next, the configuration of an electric power steering device to which the inverter control device 200 according to one embodiment of the present invention is applied will be described with reference to FIG.

[0072] FIG. 9 is a configuration diagram of an electric power steering device to which the inverter control device 200 according to one embodiment of the present invention is applied.

[0073] 9, the electric actuator of the electric power steering is composed of a torque transmission mechanism 902, a motor 300, an inverter 100, and an inverter control device 200. The electric power steering device includes an electric actuator, a steering wheel (steering wheel) 900, a steering detector 901, and an operation amount command device 903, and has a configuration in which the operating force of the steering wheel 900 steered by the driver is torque-assisted using the electric actuator.

[0074] The torque command τ* of the electric actuator is generated by an operation amount command device 903 as a steering assist torque command for the steering wheel 900. The driver's steering force is reduced using the output of the electric actuator driven by the torque command τ*. The inverter control device 200 receives the torque command τ* as an input command, and controls the operation of the inverter 100 to control the current flowing through the motor 300 so that the torque command τ* follows the torque command value based on the torque constant of the motor 300 and the torque command τ*.

[0075] The motor output τm output from the output shaft directly connected to the rotor of the motor 300 transmits torque to a rack 910 of the steering device via a torque transmission mechanism 902 using a reduction mechanism such as a worm, a wheel, or a planetary gear, or a hydraulic mechanism. The torque transmitted to the rack 910 reduces (assists) the steering force (operation force) of the driver's handle 900 by electric power, and the steering angle of the wheels 920, 921 is manipulated.

[0076] This assist amount is determined as follows: A steering detector 901 incorporated in the steering shaft detects the steering angle and steering torque, and an operation amount commander 903 calculates a torque command τ* taking into account state variables such as the vehicle speed and road surface condition.

[0077] The inverter control device 200 according to one embodiment of the present invention has an advantage that vibration and noise can be reduced by averaging the output voltage of the inverter 100 even when the motor 300 rotates at high speed.

[0078] 10 is a diagram showing an electric vehicle 600 to which the inverter control device 200 according to the present invention is applied. The electric vehicle 600 has a power train in which the motor 300 is applied as a motor / generator.

[0079] A front wheel axle 601 is rotatably supported at the front of the electric vehicle 600, and front wheels 602, 603 are provided at both ends of the front wheel axle 601. A rear wheel axle 604 is rotatably supported at the rear of the electric vehicle 600, and rear wheels 605, 606 are provided at both ends of the rear wheel axle 604.

[0080] A differential gear 611, which is a power distribution mechanism, is provided in the center of the front axle 601, and distributes the rotational driving force transmitted from the engine 610 via a transmission 612 to the left and right front axles 601. The engine 610 and the motor 300 are mechanically connected via a belt that is stretched between pulleys provided on the crankshaft of the engine 610 and pulleys provided on the rotating shaft of the motor 300.

[0081] This allows the rotational driving force of motor 300 to be transmitted to engine 610, and the rotational driving force of engine 610 to motor 300. In motor 300, three-phase AC power output from inverter 100 under the control of inverter control device 200 is supplied to a stator coil of a stator, whereby the rotor rotates and generates a rotational driving force according to the three-phase AC power.

[0082] That is, the motor 300 is controlled by the inverter control device 200 to operate as an electric motor, and also operates as a generator that generates three-phase AC power by receiving the rotational driving force of the engine 610 and rotating its rotor.

[0083] The inverter 100 is a power conversion device that converts DC power supplied from a high-voltage battery 622, which is a high-voltage (42 V or 300 V) power source, into three-phase AC power, and controls the three-phase AC current flowing through the stator coil of the motor 300 based on an operation command value and the magnetic pole position of the rotor.

[0084] The three-phase AC power generated by the motor 300 is converted to DC power by the inverter 100 and charges the high-voltage battery 622. The high-voltage battery 622 is electrically connected to a low-voltage battery 623 via a DC-DC converter 624. The low-voltage battery 623 constitutes a low-voltage (14v) system power source for the electric vehicle 600, and is used as a power source for a starter 625 that initially starts (cold starts) the engine 610, a radio, lights, etc.

[0085] When the electric vehicle 600 is stopped (idle stop mode), such as when waiting at a traffic light, the engine 610 is stopped, and when the engine 610 is to be restarted (hot start) when the vehicle is to be driven again, the motor 300 is driven by the inverter 100 to restart the engine 610.

[0086] In the idle stop mode, if the charge level of high voltage battery 622 is insufficient or if engine 610 is not sufficiently warmed up, engine 610 continues to run without being stopped. In addition, in the idle stop mode, it is necessary to secure a drive source for accessories that use engine 610 as a drive source, such as an air conditioner compressor. In this case, motor 300 is driven to drive the accessories.

[0087] Even in an acceleration mode or a high-load operation mode, the motor 300 is driven to assist the driving of the engine 610. Conversely, in a charge mode in which the high-voltage battery 622 needs to be charged, the engine 610 causes the motor 300 to generate power to charge the high-voltage battery 622. That is, the motor 300 is operated in a regenerative manner when the electric vehicle 600 is braking or decelerating.

[0088] The electric vehicle 600 includes an inverter control device 200 that generates PWM pulses for converting a DC voltage to an AC voltage based on a motor output request, an inverter 100 that converts a DC voltage to an AC voltage by the generated PWM pulses to drive a motor 300, and a DC / DC converter 624 that boosts the DC voltage. The inverter control device 200 generates a PWM pulse signal Pr using a single pulse generation logic in a control mode in which the carrier wave Tr is synchronized with the rotation speed ωr of the motor 300 from an asynchronous PWM in which the rotation speed ωr of the motor 300 is asynchronous to the asynchronous PWM, and a synchronous 1 pulse in which the carrier wave Tr is asynchronous to the rotation speed ωr of the motor 300, and reduces the output voltage error of the inverter in an operating state in which the number of PWM pulses is small. This makes it possible to reduce the DC components and low-order harmonic components of the motor current generated in the zero-cross vicinity region, thereby achieving low noise and low vibration of the electric vehicle 600.

[0089] The inverter control device according to the present invention described above provides the following advantageous effects.

[0090] (1) The inverter control device 200 of the present invention includes a PWM pulse generating unit 250 that generates a PWM pulse signal Pr for controlling the inverter 100 at every predetermined control period. The PWM pulse generating unit 250 generates a PWM pulse signal Pr asynchronous with the control period while satisfying the pulse generation conditions that at least three or more pulses exist in one period of the fundamental wave of the output voltage of the inverter 100, and the on / off state of the PWM pulse signal Pr switches at the zero crossing point where the fundamental wave changes across zero. In this way, it is possible to reduce the DC component and low-order harmonic component of the inverter output current generated in the region near the zero crossing. As a result, it is possible to reduce the DC component and low-order harmonic component of the inverter output current generated in the operating state of the motor where the number of PWM pulses is reduced.

[0091] (2) In the inverter control device 200 of the present invention, the PWM pulse generating unit 250 calculates the modulation factor MF of the inverter output voltage (step S1), and sets each pulse width of the PWM pulse signal Pr based on the modulation factor MF (step S2). In this way, the PWM pulse signal Pr can be easily generated by calculation processing using a microcomputer or the like.

[0092] (3) The PWM pulse generating unit 250 includes a modulation factor calculation unit 51 that calculates the modulation factor MF, a pulse phase angle calculation unit 53 that calculates a pulse phase angle α for switching the on / off state of the PWM pulse signal Pr based on the modulation factor MF, a voltage phase calculation unit 54 that calculates a voltage phase θv according to the phase angle of the inverter output voltage, a phase change width calculation unit 55 that calculates a phase change width Δθ of the inverter output voltage in a control period of the inverter control device 200, and a pulse setting unit 56 that sets the timing of switching the on / off state of the PWM pulse signal Pr based on the pulse phase angle α, the voltage phase θv, and the phase change width Δθ. As a result, the generation of the PWM pulse signal Pr that satisfies the above-mentioned pulse generation conditions can be realized by calculation processing using a microcomputer or the like.

[0093] (4) The inverter 100 is connected to the motor 300. The PWM pulse generating unit 250 selectively outputs either a first PWM pulse signal (asynchronous pulse signal P) that satisfies the above-mentioned pulse generation condition based on the operating state of the motor 300, or a second PWM pulse signal (synchronous pulse signal P') based on a comparison between a voltage command (Vd*, Vq*) for the inverter 100 and a carrier signal (carrier wave Tr) that changes periodically with a predetermined carrier period Tc (steps S8 to S12). As a result, an optimal PWM control mode is selected based on the operating state of the motor 300, and a PWM pulse signal Pr corresponding to the selected PWM control mode is output from the PWM pulse generating unit 250 to the drive signal generating unit 260, so that the inverter 100 can be controlled.

[0094] (5) The PWM pulse generating unit 250 generates the PWM pulse signal Pr so that the number of pulses present in one period of the fundamental wave of the inverter output voltage is an odd number. This makes it possible to generate a PWM pulse signal Pr that can reliably reduce the low-order harmonic components of the inverter output voltage.

[0095] Although the electric vehicle 600 in the embodiment is a hybrid vehicle, the same effects can be obtained in plug-in hybrid vehicles, electric vehicles, and the like.

[0096] In addition, in the above-described embodiment, the inverter control device alone has been described, but the present invention can also be applied to an inverter device in which an inverter control device and an inverter are integrated, or a motor drive system in which an inverter device and a motor are integrated, so long as the device has the above-described functions.

[0097] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0098] 1...Motor device 2. Battery 51...Modulation rate calculation section 52...Rotational speed calculation unit 53...Pulse phase angle calculation section 54...Voltage phase calculation section 55...Phase change width calculation section 56...Pulse setting section 57...dq / three-phase conversion section 58…Carrier wave calculation section 59…PWM control unit 60…PWM control mode determination section 100...Inverter 200...Inverter control device 210...Current control unit 250…PWM pulse generator 260...Drive signal generating unit 270...Rotational position detection unit 280…Current detection section 300…Motor 320...Rotational position sensor 600…Electric vehicle

Claims

1. A PWM pulse generating unit generates a PWM pulse signal for controlling an inverter, The PWM pulse generating unit selects either a synchronous mode or an asynchronous mode, and in the asynchronous mode, generates the PWM pulse signal so as to satisfy the pulse generation conditions that at least three or more pulses exist in one period of the fundamental wave of the output voltage of the inverter, and the on / off state of the PWM pulse signal switches at the zero-crossing point where the fundamental wave changes across zero.

2. 2. The inverter control device according to claim 1, The PWM pulse generating unit calculates a modulation factor of the output voltage and sets each pulse width of the PWM pulse signal based on the modulation factor.

3. 3. The inverter control device according to claim 2, The PWM pulse generating unit is A modulation factor calculation unit that calculates the modulation factor; a pulse phase angle calculation unit that calculates a pulse phase angle for switching an on / off state of the PWM pulse signal based on the modulation factor; a voltage phase calculation unit that calculates a voltage phase according to a phase angle of the output voltage; a phase change width calculation unit that calculates a phase change width of the output voltage in a predetermined control period; a pulse setting unit that sets a switching timing for switching the on / off state of the PWM pulse signal based on the pulse phase angle, the voltage phase, and the phase change width.

4. 2. The inverter control device according to claim 1, The inverter is connected to a motor, The PWM pulse generating unit is an inverter control device that selects either the synchronous mode or the asynchronous mode based on an operating state of the motor.

5. 2. The inverter control device according to claim 1, The inverter control device, wherein the PWM pulse generating unit generates the PWM pulse signal so that the number of pulses present in one period of a fundamental wave of the output voltage is an odd number.

6. An inverter control device according to any one of claims 1 to 5; The inverter controlled by the inverter control device; an AC motor driven by the inverter, An electric power steering system that uses the AC motor to control the steering of a vehicle.

7. An inverter control device according to any one of claims 1 to 5; The inverter controlled by the inverter control device; an AC motor driven by the inverter, An electric vehicle system that runs using the driving force of the AC motor.

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